Internal obturator muscle: Proposition of a transforaminal way under ultrasound guidance for botulinum toxin injections

Abstract

Among pelvitrochanteric muscles, the internal obturator muscle is implicated in some pain projected at the buttock or perineum. Even though the pathophysiology is not completely understood, its responsibility is often held in clinical practice and in the literature due to effectiveness of botulinum toxin injections, constituting a therapeutic test. The objective is to enhance the couple ultrasound/EMG in difficult injections. Eighteen patients were treated in the physical medicine department (Besançon) from September 2015 to February 2016 for gluteal or perineal pain suspected to be related to abnormal spasm of the internal obturator muscle. All patients had a normal MRI of the pelvis. They received an injection of botulinum toxin associated with an anesthetic in the internal obturator muscle under ultrasound and electromyographic guidance. There were 11 women and 7 men (mean age 57 years). The effectiveness of botulinum toxin injections cannot be evaluated because some of the patients were included as part of a national study (PHRC) whose results are not yet known. Regarding the gesture as such, the tolerance is good with, visual analog scale (VAS) is given to 3.1 [1.5–7] in the immediate aftermath of the injection, and 2.8 [1–6.5] to the memory of the injection gesture during a new evaluation 6 to 8 weeks later. It has not been described complication (no hematoma, any orthopedic, visceral or neurological disorders have been reported). Botulinum toxin injections into the internal obturator muscle can be performed under CT control, the patient is placed in the prone position. The aim is to achieve the muscular endopelvic part. This position does not allow under ultrasound guidance to follow the end of the needle, which is why we developed the transforaminal approach of injection in gynecological position. The clinical tolerance of this gesture is good and the images are of very good quality to optimize and secure this type of injection. The couple ultrasound/EMG is available to the clinician and should be enhanced to guide some injections especially for deep sites.